Set up a Geofence Reminder on Your iPhone

When iOS 5 was released, Apple introduced geofences, the ability to detect proximity to a geographic location. Today, in iOS6 with the Reminders app, users can set up a reminder so that when they enter or leave a geographic location, they'll get a notification on their iPhone. Here's how to do it.

What You'll Need

You need to be using an iPhone 4 or later. iOS 6 or later with the Reminders app is recommended. iPads, even those with cellular and GPS, currently do not have this feature enabled. (There's more on that below.)

Why Would I Use it?

Setting up a geofence can come in handy when you want to remind yourself to buy something the next time you're at the grocery store. Or you may want to set up a reminder to ask someone a quesion the next time you visit them. Another use is to set up a standard departure reminder when you leave the house: checkbook? sunglasses? (Or, in the event of a restraining order...)

How-to

The following example will show you how to set up a reminder for when you arrive at a specific geographic location. The idea is that there's a virtual perimeter set up around a geographic location, and when you penetrate the perimeter, you'll get an alert. Start by locating the Reminders app on your iPhone and follow these steps.

Tap the Reminders app on your iPhone.

Tap the "+" button on the top right.

Enter text label for your reminder.

Tap the ">" symbol to the right of the text.

Set "Remind Me At a Location" to ON.

Tap the default location below that. You'll see a candidate list of locations. If you don't see what you want, you can 1) enter an address manually or 2) tap the white "+" in the blue circle to select an address that's already in your Contacts.

Under the "Notes" field, enter the details of the alert. Say, something you wanted to buy at that location.

Tap to select the entry "When I arrive." Set a priority of you wish.

Tap the Done button on the top right.

When you're finished, it should look like this:

Now, when you approach that geographic location, you'll get an alert sound and a Notification popup.

Note: the text in this alert was from a different alert
than the one set up here.

Then you can view your reminder by tapping "View."

You can also set up the geofence to alert you when you leave a location in the same manner. In that case, you'd select, instead, "When I Leave" in Step #8 above. See the note below regarding the "trip" distance.

If you cross this perimeter, you'll get an alert.

Technical Notes

Geofencing requires the use of iOS Location Services. Location Services uses a cascade rollover technique. First, it looks for a nearby Wi-Fi hotspot of a known location. That's fast. Next, if the device has a cellular radio, it will try triangulating from cell towers. Finally, if the system needs more accuracy, or can't find a hotspot or cell tower, it will turn on the GPS radio for a better fix.

Not every iDevice has a cellular radio. All iPhones do. Those that do, also have GPS, such as iPads with cellular. However, Apple has chosen not to enable geofencing on any iPad model. I asked developer Andrew Stone of Stone Design Software about that, and he told me, "I wonder if, to avoid confusion, and to reflect the fact that most of their iPad sales are not the Wi-Fi + Cellular but just the vanilla Wi-Fi, they didn't enable that feature on the iPad. That's of course terrible from a consumer perspective since they bought the 'Cadillac,' [of iPads] but understandable from a support side concern."

In other words, it could be that Apple believes that the full size iPads are not candidate device for these kinds of geofence alerts because of the way they're carried about and used. However, Mr. Stone noted that the introduction of the iPad mini that can fit in a purse or cargo pants may undermine that assumption.

In terms of the "trip" distance, Mr. Stone pointed me to Apple developer documentation that says:

The specific threshold distances are determined by the hardware and the location technologies that are currently available. For example, if Wi-Fi is disabled, region monitoring is significantly less accurate. However, for testing purposes, you can assume that the minimum distance is approximately 200 meters."

The combination of hardware technologies available, their efficiency, battery power, cell tower strength, the GPS chip used, access to the sky and so on will likely cause some variation in the "trip" threshold. In my own testing with an iPhone 5 in wide open spaces, the threshold seemed to be about 100 meters. Some users with older iPhones, back to the iPhone 4, have reported varying results.

Finally, the monitoring necessary to detect a perimeter penetration requires significant battery power. Everyone who has used this feature has reported that battery life is adversely affected.

You can confirm that Location Services is continuously working by noting the flag at the top of the iPhone's display, next to the battery power. Once you delete the (last) location-based reminder, all else being equal, that flag will disappear, reducing the drain on the battery. Use this feature with care when you need to conserve power.